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Oysters — Part 4

The famous French "green oysters" of Marennes are carefully fattened in ponds containing a green diatom whose pigment colours the gill fringes to the shade required by an exacting public, and gives the oyster their distinctive flavour. English people and Americans frankly dislike green oysters.

The British oyster market is supplied from beds about the mouth of the Thames and off the coasts of Kent and Essex. The Englishman prefers a five-inch "native," five years old. In New York oysters are marketed at from three years old upward.

Oysters are fattened on bran and oatmeal in cellar tanks for the Billingsgate market in London. "The flavour is all but lost in the fat." Experiments prove our oysters to fatten and improve in flavour by being liberally supplied with fine corn meal. This is not practicable; the natural food supply brings the oyster to prime condition, and extra fatness is not demanded by the American market.

The best fattening grounds are often found near the mouths of rivers, in brackish water. It is true that by reason of the pollution of streams by sewage, oysters are contaminated, and typhoid and cholera sometimes develop in persons eating these oysters. "Oyster scares" are periodic outbreaks that for a time check local demand. The laying down in clean water of oysters from muddy beds greatly improves their appearance and flavour, by the thorough washing it accomplishes.

The Oyster's Enemies.--It is calculated that an infant oyster has but one chance in one million one hundred and forty-five thousand to grow up. Fish devour the larvae in great numbers. Settled comfortably on the shell or stone that is to be its support for life, and shielded to an increasing extent by its own shell, the oyster may bid farewell to many fears that beset its free-swimming infancy. But enemies are present in great variety and numbers still. A freshet may cause deposits of mud that smother them; the currents may shift the sand just enough to bury them. Crabs many times devastate an oyster bed, as if by concerted action, crushing all young shells up to a year old with their powerful pincers. The starfish, ray and octopus do great damage. Drills (Urosalpinx) and dog whelks (Nassa) are enemies which bore the shells with their rasping tongues and suck out the soft parts, leaving the tough remains for the scavenger crabs and whelks. The moon shell (Natica) and pear conch (Fulgur), are charged with similar deeds, but they are not such oyster specialists as the well-hated and hotly pursued drills.

Fish consume young oysters until the shells are hard enough to resist their horny jaws. The drumfish and sheepshead menace the beds about Long Island. Menhaden and alewife are in this same predatory class.

One of the most insidious enemies is the boring sponge which honeycombs the shells so that the oyster is exhausted with sealing up punctures with new shell deposits. Often these shells crumble. They form stations for the attachment of sponges and hydroids, which smother the oyster, and rob it of food.

The starfish begins its ravages upon oysters scarcely the size of a pin head, and continues through life. It swallows the spat, and oysters up to three inches long. Its stomach is turned wrong side out, and often wrapped around the victim, which is overcome by the digestive fluids. The flexible arms clasp the oyster shell, adhering by means of their rows of sucking disks. Dr. Schiemenz believes the star actually forces apart the valves of large shells by main strength. It holds on until the victim's strength is gone, then thrusts its inverted stomach into the interior and absorbs the contents.

Starfishes go in schools, migrating from place to place, destroying the victims in their path. In brackish water they do little harm, but in outside beds destruction may be complete before the owner suspects that anything is wrong.

The "tangle," a great mop made of bunches of ravelled rope, supported on iron rods, is let down from a vessel, by davitts with block and fall, and drawn across the oyster beds. Stars of varying sizes are brought up, entangled in its meshes. The best equipped boats have a trough of water heated by connection with the boiler of the engine. Into this the mops are plunged. It kills the stars, and the tangle is lowered again. With this labour and time saving device, using two tangles, alternately hauled, over one hundred thousand starfishes have been gathered in a single day. A bed is not considered safe to leave as long as half a bushel of stars can be caught in a day.

Drills are so small as to make their capture very difficult. An eye out for drills is a prime necessity in dredging and culling. The tangle gets a few, but this is incidental. A dredge with fine screen sides and bottom, and lid of inch mesh screen has a sharp iron lip. Dragged along the bottom, this scoops up everything that is loose; the drills and other small debris fall into the dredge, the coarse material passes over the lid, and is left behind. The dredge is drawn up, and the drills destroyed.